Conventionally, for blood purification for, for example, renal function insufficiency patients, medical treatments by continuous blood purification methods such as Continuous Hemofiltration (CHF), Continuous Hemodia (CHD), and Continuous Hemodiafiltration (CHDF) have been performed. A blood perfusion speed of such a continuous blood purification method is lower than conventional hemodialysis, which can realize slower blood purification.
In the continuous blood purification methods, it is necessary to take a balance between (i) a flow rate of blood taken from a patient and (ii) a flow rate of blood returned to the patient and a replacement fluid injected into the patient. The balance is achieved by measuring respective used amounts of the dialysis fluid, the replacement fluid, and the filtrate, independently (refer to Patent Reference 1, for example).    Patent Reference 1: Japanese Patent No. 3180309